This invention relates generally to fireplace-type heaters, and more particularly to steam-utilizing devices of this type which improve the efficiency of a conventional fireplace without substantial modification of the basic structure thereof.
In the past, a number of systems have been proposed and produced for improving the efficiency of domestic fireplaces. Various gratings having ventilating passages, together with simple forced air devices, have become popular in recent times. While some of these have met with moderate success, there are several disadvantages to such arrangements. First, such grates remove heat from the coals and hence the fire itself, which tends to reduce the combustion temperature of the fire and thus impair the overall efficiency of the reaction. Second, no provision is typically made for limiting the flow of air into the fire. Experiments have shown that there exists an optimum air flow for a particular size fire, with flows beyond this optimum value doing nothing constructive but instead merely cooling the reaction, which actually decreases the combustion efficiency. Maximum combustion efficiency in BTU/pound of fuel occurs with the optimum (not maximum) air flow mentioned above. Most prior devices have not been able to restrict the air flow to a fire, in order to arrive at such an optimum efficiency.
Plate glass enclosures for fireplaces have had the disadvantage that the single-thickness glass became excessively heated from a large or hot fire. The natural convection from the room has been, in many cases, insufficient to maintain the glass temperature at a safe level. In addition, much of the heat from the glass and frame was merely re-radiated back into the walls of the fireplace, with a consequent loss of the useful heat available to the room.